Proportional fair scheduler for OFDMA wireless systems with QOS constraints

Abstract

Available bandwidth and power for users demanding real time and non-real time data traffic are scheduled, while maximizing proportional fairness for the users over a plurality of time slots, and meeting quality of service constraints for real time data traffic users. The Lagrangian multipliers are used to define a function which includes the proportional fair capacity over the plurality of time slots, and the total power, the total bandwidth, and rate of the real time users' constraints. A maximum of the function is determined for each time slot by binary searching two parameters while observing the total power and total bandwidth. An optimal allocation of the bandwidth and power for the time slot is calculated using the two parameters.

1. A multicarrier wireless communication apparatus supporting real time and/or non-real time data traffic for users, comprising:
 a controller that performs
 for each time slot binary searching two parameters maximizing a function that includes
 a proportional fairness over a plurality of time slots, the proportional fairness being a sum of logarithms of user rates, and 
 a total power, a total bandwidth and rate constraints for real time data traffic users, using Lagrangian multipliers, 
 
 while distributing the total power and the total bandwidth to all the users, and 
 calculating optimal signal to noise ratio values, optimal bandwidth values and optimal power values corresponding to each user based on the two parameters. 
 
 
   
   
     2. The apparatus of  claim 1 , wherein the controller estimates whether the optimal signal to noise ratio values, optimal bandwidth values and optimal values for the users exist, before performing binary searching. 
   
   
     3. The apparatus of  claim 2 , wherein the controller drops some users if the optimal signal to noise ratio values, optimal bandwidth values and optimal values for the users does not exist. 
   
   
     4. The apparatus of  claim 1 , wherein the binary search finds first one of the two parameters while the other one of the two parameters is zero, the total bandwidth being distributed, then iteratively performs binary searches of the two parameters, the total bandwidth and the total power being distributed. 
   
   
     5. The apparatus of  claim 1 , wherein the controller determines discrete bandwidth values and discrete power values based on quantizing the optimal bandwidth values and the optimal power values to allowed values. 
   
   
     6. The apparatus of  claim 5 , wherein the controller determines the discrete bandwidth values and discrete power values using the highest modulation and coding scheme allowed. 
   
   
     7. The apparatus of  claim 1 , wherein the rate constraints ensure a minimal transmission rate and a limited delay for non-real time data. 
   
   
     8. A method of allocating a total bandwidth and a total power to users performing non-real time data and/or real time traffic, in each time slot, in a wireless multicarrier apparatus, comprising:
 using a computer binary searching two parameters that maximize a function that includes
 a proportional fair capacity over a plurality of time slots, the proportional fair capacity is a sum of logarithms of user rates, and 
 limitations on the total power, the total bandwidth, and rate of users performing real-time traffic, using Lagrangian multipliers; and 
 
 calculating a power value and a bandwidth value for each user using the determined two parameters. 
 
   
   
     9. The method of  claim 8 , further comprising:
 estimating whether allocating the total bandwidth and the total power to users has a feasible solution before determining the two parameters. 
 
   
   
     10. The method of  claim 8 , wherein the binary search includes
 binary searching one of the two parameters while the other one of the two parameters is zero, with the total bandwidth being distributed, and 
 iteratively performing binary searches of the two parameters, with the total bandwidth and the total power being distributed. 
 
   
   
     11. The method of  claim 8 , where the optimal bandwidth and power values are quantized to match allowed bandwidth and power values. 
   
   
     12. A computer readable medium storing executable codes which make a computer to execute operations of allocating a total bandwidth and a total power to users communicating non-real time data and/or real traffic, in each time slots, by:
 binary search two parameters, while observing limitations on the total power and the total bandwidth, wherein the two parameters maximize a function that includes 
 a proportional fair capacity over a plurality of time slots, the proportional fair capacity is a sum of logarithms of user rates, and 
 the limitations on the total power, the total bandwidth, and rates of users performing real-time traffic, by using Lagrangian multipliers; and 
 calculating power values and bandwidth values for the users using the determined two parameters. 
 
   
   
     13. The computer readable medium of  claim 12 , the method further comprising:
 estimating whether allocating the total bandwidth and the total power to users has a feasible solution, before determining the two parameters. 
 
   
   
     14. The computer readable medium of  claim 12 , wherein the binary search includes
 finding one of the two parameters while the other one of the two parameters is zero, with the total bandwidth being distributed, and 
 iteratively performing binary searches of the two parameters, with the total bandwidth and the total power being distributed. 
 
   
   
     15. The computer readable medium of  claim 12 , where the optimal bandwidth and power values are quantized to match allowed bandwidth and power values.